Analysing Motifs in Multilayer Networks

TL;DR

This paper extends the concept of network motifs to multilayer networks, providing a formal definition and analyzing their occurrence in real-world social, transportation, and biological networks to reveal underlying interaction patterns.

Contribution

It introduces a formal definition of multilayer motifs and analyzes their occurrence in real-world networks, highlighting differences across social, transportation, and biological systems.

Findings

Social network motifs are more homogeneous across layers.

Transportation network motifs are more complementary across layers.

Biological networks often show heterogeneous functions.

Abstract

Network motifs can capture basic interaction patterns and inform the functional properties of networks. However, real-world complex systems often have multiple types of relationships, which cannot be represented by a monolayer network. The multilayer nature of complex systems demands research on extending the notion of motifs to multilayer networks, thereby exploring the interaction patterns with a higher resolution. In this paper, we propose a formal definition of multilayer motifs, and analyse the occurrence of three-node multilayer motifs in a set of real-world multilayer networks. We find that multilayer motifs in social networks are more homogeneous across layers, indicating that different types of social relationships are reinforcing each other, while those in the transportation network are more complementary across layers. We find that biological networks are often associated with heterogeneous functions. This research sheds light on how multilayer network framework enables the capture of the hidden multi-aspect relationships among the nodes.